validation: Move GetLastCheckpoint to BlockManager

[META] This commit should be followed up by removing the comments and
       assertions meant only to show that the change is correct.

GetLastCheckPoint mainly acts on BlockManager.

Author: dongcarl

src/validation.cpp

@@ -3401,15 +3401,15 @@ std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBloc
     return commitment;
 }
 
-//! Returns last CBlockIndex* that is a checkpoint
-static CBlockIndex* GetLastCheckpoint(const CCheckpointData& data) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
+CBlockIndex* BlockManager::GetLastCheckpoint(const CCheckpointData& data)
 {
     const MapCheckpoints& checkpoints = data.mapCheckpoints;
 
     for (const MapCheckpoints::value_type& i : reverse_iterate(checkpoints))
     {
         const uint256& hash = i.second;
-        CBlockIndex* pindex = g_chainman.m_blockman.LookupBlockIndex(hash);
+        assert(std::addressof(g_chainman.m_blockman) == std::addressof(*this));
+        CBlockIndex* pindex = LookupBlockIndex(hash);
         if (pindex) {
             return pindex;
         }
@@ -3441,7 +3441,7 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, BlockValidatio
         // Don't accept any forks from the main chain prior to last checkpoint.
         // GetLastCheckpoint finds the last checkpoint in MapCheckpoints that's in our
         // BlockIndex().
-        CBlockIndex* pcheckpoint = GetLastCheckpoint(params.Checkpoints());
+        CBlockIndex* pcheckpoint = g_chainman.m_blockman.GetLastCheckpoint(params.Checkpoints());
         if (pcheckpoint && nHeight < pcheckpoint->nHeight) {
             LogPrintf("ERROR: %s: forked chain older than last checkpoint (height %d)\n", __func__, nHeight);
             return state.Invalid(BlockValidationResult::BLOCK_CHECKPOINT, "bad-fork-prior-to-checkpoint");

src/validation.h

@@ -40,6 +40,7 @@ class CBlockIndex;
 class CBlockTreeDB;
 class CBlockUndo;
 class CChainParams;
+class CCheckpointData;
 class CInv;
 class CConnman;
 class CScriptCheck;
@@ -433,6 +434,9 @@ class BlockManager
     /** Find the last common block between the parameter chain and a locator. */
     CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
+    //! Returns last CBlockIndex* that is a checkpoint
+    CBlockIndex* GetLastCheckpoint(const CCheckpointData& data) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
     /**
      * Return the spend height, which is one more than the inputs.GetBestBlock().
      * While checking, GetBestBlock() refers to the parent block. (protected by cs_main)